JPH0455336A - Production of glass particulate deposit - Google Patents

Abstract

PURPOSE:To improve the deposition efficiency by forcedly cooling the surface of a rotating target out of direct contact with a flame during the deposition of glass particulates. CONSTITUTION:A metal halide such as SiCl4 forming a glass and a carrier gas of Ar, etc., are introduced into the oxygen flame of a burner 3 and oxidized in the flame to form oxide quartz glass particulates 31. The particulates 31 are blown against the side surface of a target 1 horizontally held and rotating around the center axis at about 40 r.p.m. In this case, a water current 41 is injected against the side surface of the target out of direct contact with the flame from a water cooling nozzle 4 arranged close to the target 1 and moving along with the reciprocation of the burner 3 to forcedly cool the surface. Since the burner 3 is reciprocated in the longitudinal direction of the target 1, the particulates 31 are deposited on the entire side surface of the target 1, and the deposit 5 of glass particulates is obtained with good efficiency.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method of manufacturing an optical fiber base material made of glass, and in particular to a method of producing a glass particle deposit by generating glass particles using a gas phase reaction and depositing them on a target. Regarding improvements.

[Conventional technology]

Conventionally, glass particles are generated using a gas phase reaction, deposited on a target to create a glass particle deposit, and this glass particle deposit is heated at high temperature to create a transparent glass lump (optical fiber matrix). Optical fibers are produced by drawing and spinning this glass block. In this case, various manufacturing methods are conventionally known as methods for manufacturing a glass particle deposit for obtaining an optical fiber base material. Among them, the so-called VAD method (vapor phase deposition method for shaft attachment) and OVD method (vapor phase deposition method for external attachment) are capable of producing large optical fiber base materials, and are suitable for manufacturing glass particle deposits suitable for mass production. known as the method. In the former VAD method, as shown in FIG. 6, a metal halide such as silicon tetrachloride, which is a raw material for glass, is introduced into a plurality of burners 3, glass fine particles are generated in the flame, and the glass fine particles are Target 1 or starting member 2 (
and the lower end of the glass fine particle deposit 5) thereon to form the glass fine particle deposit 5. This glass particle deposit 5 is then heated in a heating furnace 6 to become transparent, and is used as an optical fiber base material 7. In the latter OVD method, as shown in FIG. 7, a metal halide such as silicon tetrachloride, which is a raw material for glass, is introduced into the burner 3, glass fine particles are generated in the flame, and the glass fine particles are transferred to the target 1. That is, the glass fine particle deposit 5 is formed by adhering to the side surface of the starting member 2 (and the glass fine particle deposit 5 thereon). This glass particle deposit 5 is hollowed out from the starting member 2 and is then heated in a heating furnace 6 to be made transparent and used as an optical fiber base material 7. When the starting member 2 is made of glass that will later become the core, the starting member 2 is heated and made transparent without being hollowed out and containing the starting member 2. The manufacturing method of these glass fine particle deposits basically consists of: ■ Introducing a metal halide such as silicon tetrachloride into a flame such as an oxyhydrogen flame, and converting the oxide into an oxide through a thermal oxidation reaction or flame hydrolysis reaction. The method involves generating glass particles, then spraying the above-mentioned flame onto the side or bottom surface of a rotating target, and continuously depositing the generated glass particles on the side or bottom surface of the rotating target. be. In such a glass particle deposition process, the mechanism of particle deposition is said to be dominated by deposition accompanied by material transfer due to a so-called temperature gradient (thermophorhesi, s). That is, in order for the glass particles to be efficiently deposited on the target, it is necessary that the temperature of the flame is sufficiently high, while the target 1 to surface is cold and the temperature gradient therebetween is high. VAD method and O
The VD method differs in the positional relationship between the target and the flame (burner) as described above, but this Thergnopho
From the viewpoint of rhesis, these positional relationships are considered to be essentially the same.

[Problems to be Solved by the Invention] However, in the conventional method for manufacturing a glass particle deposit as described above, there is a problem in that the adhesion efficiency of glass particles is poor. In other words, when glass particles are actually deposited using the method described above, the proportion of glass particles that are actually collected on the target compared to the total amount of glass particles that are theoretically generated is, on average, at most. Currently, it is about 50%, and in bad conditions it is so low that it can go as high as 30%. This is because in order to collect the glass particles generated by the burner with a certain degree of efficiency, the burner must be brought closer to the target, and when the burner is brought closer, the target temperature increases, making it possible to collect the glass particles more efficiently This is due to the dilemma that a suitable temperature gradient cannot be obtained. In view of the above, an object of the present invention is to provide a method for manufacturing a glass particle deposit body, which is improved so as to improve the adhesion efficiency of glass particles and is suitable for mass production of optical fibers. [Means for Solving the Problems] In order to achieve the above object, according to the present invention, glass fine particles are generated in a flame, and the glass fine particles are blown toward a rotating target so that the glass fine particles are blown onto the target. A method for manufacturing a glass particle deposit body in which a glass particle deposit is deposited is characterized in that during the deposition, a surface of the rotating target that is not directly hit by the flame is forcibly cooled.

[For production]

Glass particles are generated in the flame and blown toward a rotating target, causing the glass particles to adhere to the target surface. On the other hand, the surface of the rotating target on the side that is not directly hit by the flame is forcedly cooled by being sprayed with liquid cooling water or mist cooling water. Therefore, the part of the target that is hit by the flame is continuously supplied with a surface that is always forcibly cooled and in a cold state. As a result, the temperature gradient between the flame and the target is increased, and the efficiency with which the glass particles blown onto the target adhere to the target surface is improved.

【Example】

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. Figure 1 shows an embodiment in which the present invention is applied to the OVD method. In this figure, combustion gas such as oxygen or hydrogen is fed into the burner 3 to generate an oxyhydrogen flame. A metal halide, which serves as a raw material for glass, such as hydrogen tetrachloride gas, is fed into the flame together with a carrier gas such as argon gas. This metal halide ~ is oxidized in a flame to produce oxide quartz glass particles. The glass particle flow 31 thus formed in the flame is blown onto the side surface of the target 1. The target 1 is held horizontally and rotated around its central axis at, for example, 40 revolutions per minute, and the burner 3
is made to reciprocate (traverse) in the length direction of this target 1. Therefore, glass particles adhere and accumulate all around the side surface of the target 1. The configuration up to this point is the same as the normal OVD method, but according to the present invention, a cooling device for forcibly cooling a part of the target 1 is added. That is, several water cooling nozzles 4 are arranged near the target 1 and are traversed along with the traverse of the burner 3, and the water cooling nozzles 4 are placed on the side of the rotating target 1 that is not directly hit by the flame. A water stream 41 is ejected from 4 to forcefully cool that part. Initially, the target 1 is the starting member 2 itself, but when glass particles are deposited on the side surface of the starting member 2, this glass particle deposit body itself becomes the target. In this embodiment, as shown in the cross section in FIG. 2, the starting member 2 has a core glass 21 at the center which will later become the core of the optical fiber, and around it a cladding which will later become part of the cladding of the optical fiber. A glass 22 is used. Here, the core glass 21 consists of quartz glass containing, for example, about 5% by weight of germanium oxide, and the cladding glass 22 consists of substantially pure quartz glass. In this embodiment, the positional relationship among the target 1, burner 3, and water cooling nozzle 4 is as shown in FIG. Here, it is assumed that the glass fine particle deposit 5 has already been formed around the starting member 2. The water cooling nozzle 4 is positioned so that the water flow 41 from the water cooling nozzle 4 hits the surface opposite to the surface on which the glass particle flow 31 from the burner 3 hits the target 1. As a result, approximately half the surface of the target 1 on the side opposite to the side that is hit by the flame is forcedly cooled. The conditions for these burners 3 and water cooling nozzles 4 can be determined, for example, as shown in the following table 9 (SLM=Sta
Under the conditions specified in the table above, if all the glass raw materials were attached to the target 1, the glass fine particle deposit 5 would grow at a rate of 26.8 g/min. It should be done. Therefore, by measuring the weight of the target 1 being deposited, the rate of increase per hour was determined, and then the deposition efficiency was calculated, and data as plotted with the circles in FIG. 4 was obtained. As a reference example, when we performed deposition under the same conditions as above using the conventional method, that is, without using the water cooling nozzle 4, and similarly obtained data on deposition efficiency, we obtained data as plotted with the X mark in Figure 4. It became. From FIG. 4, it can be seen that in the conventional method, even if the deposition of glass particles on the target 1 progresses and reaches a certain thickness, the deposition efficiency is only 60%, and the adhesion of the glass particles to the starting member 2 is low. When the target 1 is thin and has hardly progressed, this adhesion efficiency decreases further and the diameter is 2.
It can be seen that for 511II11, it is at most 15%. On the other hand, the water flow 41 from the water cooling nozzle 4
In this example where the diameter of the target 1 was 25W, the adhesion efficiency was 22%, and when the glass particles were attached to the target 1 and the diameter of the target 1 became 150W, the adhesion efficiency was 22%. The adhesion efficiency is 8
This has increased to 3%. This is because, as shown in Fig. 3, the half of the rotating target 1 opposite to the flame is forcibly cooled by the water flow from the water cooling nozzle 4. It is thought that the adhesion efficiency was improved by increasing the temperature gradient between the flame and the target 1 because the surface of the target 1 was continuously supplied. Although the above embodiment is an application of the present invention to the OVD method, it can of course also be applied to the VAD method. V
When applied to the AD method, it becomes as shown in FIG. Fine glass particles are generated in the flame of the burner 3 for core and cladding, and deposited on the lower end of the rotating starting member 2. When the glass fine particle deposit 5 has grown, while rotating the starting member 2, pull upwards. In this way, the glass fine particle deposit 5 is grown in the axial direction of the starting member 2, and a water stream is injected from the water cooling nozzle 4 onto the surface of the target 1 opposite to the side that is hit by the flame from the burner 3. 41 for forced cooling. As a result, it was confirmed that in Example 1, the adhesion efficiency could be improved from about 45% in the conventional case without forced cooling to about 63%. In each of the above embodiments, the water stream 41 from the water cooling nozzle 4 was applied directly to the surface of the target 1 in a liquid state, but the water was made into a mist using a nebulizer and was sprayed onto the surface of the target 1. Forced cooling can also be performed by blowing on the air.

【Effect of the invention】

As described above with respect to the embodiments, according to the method for producing a glass fine particle deposit body of the present invention, it is possible to improve the deposition efficiency of glass fine particles when depositing glass fine particles in a gas phase. Therefore, large-sized optical fiber preforms can be easily manufactured, which greatly contributes to the mass production of optical fibers.

[Brief explanation of the drawing]

Fig. 1 is a perspective view schematically showing an embodiment of the present invention, Fig. 2 is a sectional view of a starting member used in the embodiment, and Fig. 3 shows the positional relationship between the target, burner, and water cooling nozzle. 4 is a graph showing the dependence of deposition efficiency on target diameter, FIG. 5 is a perspective view schematically showing another embodiment, and FIG. 6 is a schematic diagram showing the conventional VAD method. FIG. 7 is a schematic diagram showing the conventional OVD method. DESCRIPTION OF SYMBOLS 1... Target, 2... Starting member, 21... Core glass, 22... Clad glass, 3... Burner, 31... Glass fine particle flow, 4... Water cooling nozzle,
41... Water flow, 5... Glass fine particle deposit, 6...
- Heating furnace, 7... Optical fiber base material.

Claims (1)

[Claims] (1) In a method for producing a glass particle deposit body in which glass particles are generated in a flame and the glass particles are blown toward a rotating target to deposit the glass particles on the target, the rotating target is produced during the deposition. 1. A method for producing a glass particulate deposit, characterized by forcibly cooling a surface that is not directly exposed to flame.